The present invention relates to a transparency adapter for flatbed scanners, and relates more particularly to such a transparency adapter which eliminates the interference of shadows of black spots on the bottom side of the hot cathode-ray tube by using a refractor to refract light from the hot cathode-ray tube onto the document to be scanned and to prevent light from being directly projected by the hot cathode-ray tube onto the document.
When a flatbed scanner is used to scan a transparency or negative, a transparency adapter must be used. The transparency adapter has a hot cathode-ray tube, which projects light onto the document to be scanned so that the image of the document can be picked up by the CCD (charge-coupled device) of the flatbed scanner. However, because mercury steam will be condensed and deep-seated at the bottom, black spots will appear in the bottom side of the hot cathode-ray tube. When these black spots appear, the scanning quality will be affected, and the hot cathode-ray tube should be replaced.